The present invention relates to a motorized rake assembly that, in conjunction with a bar screen located in a fluid canal or channel to catch and retain debris from the flowing fluid, intermittently enters the channel to rake the bar screen and remove the trapped material. The rake assembly includes a raking arm that enters the fluid channel in a first position generally spaced from the bar screen, is forced toward the bar screen at the bottom of its travel to a second position where the rake can engage the debris, and then moves upward to raise the debris to a discharge point. In particular, the invention relates to such a raking apparatus which has a rake arm pivotably mounted from a guide rake carriage that, as the carriage is pivoted toward the bar screen at its lowest point of travel, permits the rake arm to independently pivot so that should a large obstruction be encountered, the rake arm is free to pivot away from the bar screen and remove all or part of the obstruction during each cycle of operation without damage to the raking structure.
It is necessary in many applications where a fluid or liquid such as water is confined to a channel and which has debris in the fluid which must be periodically removed from a debris catcher, such as a bar screen, to provide an automatic device for removing the debris which accumulates against the screen as necessary from time to time. These devices include some type of a rake which can be lowered into the fluid carrying channel to engage the bar screen and then moved upwardly out of the channel pulling the debris with the rake. When the rake has removed the debris totally from the liquid, some type of automatic device well known in the art, scrapes the rake free of the debris and the rake is then lowered back into the fluid where it again engages the bar screen to remove more of the accumulated debris.
One of the problems associated with the prior art apparatus is the fact that the rake is rigidly attached to a force producing device such as a counterweight which moves the rake toward the screen to remove the debris. If an obstacle is encountered in the liquid which cannot be removed in one continuous motion of the rake, the rake may be damaged by the tremendous forces that are suddenly applied to it by one force trying to move it forward and the other force trying to stop the forward movement. Also, the rake system must be stopped while the debris is removed in some other manner such as manually.
The present invention overcomes the difficulties and problems of the prior art by providing a raking apparatus which comprises a generally vertical guide frame and a carriage portion mounted thereon for guided reciprocal motion. The carriage assembly has an upper section, and a midsection rotatably coupled to the upper section. A rake arm, including the rake, is pivotally attached with the midsection. The upper section has guide rollers and carries the power source for moving the raking structure up and down to carry the rake into and out of the fluid canal. The midsection has guide rollers which follow a predetermined path to lower the rake into the fluid canal while supporting the rake in a first position generally spaced from the bar screen. The midsection is weighted to cause the rake to move to a second position toward the bar screen to engage the debris that is lodged against the screen. Because the rake and rake arm are pivotally attached to the midsection, if the rake encounters an obstacle which prevents it from moving further in the direction of the bar screen, the rake arm, and rake, pivots away from the bar screen with respect to the midsection to allow the midsection to continue its forward motion toward the bar screen without forcing the rake against the obstruction thus protecting the rake arm and rake and reducing the shock that would be applied to the raking assembly as a whole. The rake, however, is biased towards the bar screen by the midsection (as by counterweights) to freely engage the obstruction to remove it at least a portion at a time.
In addition, a single gear rack is utilized with appropriate limit switches to control the upward and downward movement of the entire structure.